The present invention relates to a magnetic recording medium. More particularly, it relates to a magnetic recording medium of which the magnetic layer has a high durability and contains magnetic particles in a good dispersion state.
In general, the magnetic layer of a magnetic recording medium is formed by applying a magnetic coating composition comprising magnetic particles, a binder and an organic solvent onto the surface of a base material such as a polyester film. Such magnetic layer is required to have a high durability since it runs slidingly in close contact with a magnetic head on recording and reproducing of the magnetic recording medium. Further, the magnetic particles in the magnetic layer are required to be uniformly dispersed so as to have a high sensitivity and a good S/N ratio.
For attaining the said requirements, the binder in the magnetic coating composition is desired to be one which can make the magnetic particles disperse well and also keep a high durability of the magnetic layer. From this viewpoint, various binders have been proposed, among which a mixture of a cellulose resin and a polyurethane resin is particularly recommendable. However, the durability brought by such mixture is still not satisfactory. In order to overcome this defect, the incorporation of non-magnetic Cr.sub.2 O.sub.3 particle into the magnetic layer has been proposed, but this proposal produces other drawbacks. That is, when Cr.sub.2 O.sub.3 particles are admixed with other components in a conventional mixing machine, such as a ball mill, over a long period of time or when a relatively large amount of Cr.sub.2 O.sub.3 particles is used for incorporation into a magnetic coating composition, the particles gel, and the dispersibility deteriorates, wherein the magnetic characteristics of the resulting magnetic recording medium are lowered.